Facilitation of spin-coat planarization over feature topography during substrate fabrication

ABSTRACT

Described herein are technologies to facilitate device fabrication, especially those that involve spin-on coatings of a substrate (e.g., wafer). More particularly, technologies described herein facilitate the planarization (i.e., flatness) of spin-on coatings during the device fabrication to form a uniformly planar film or layer on the substrate. This abstract itself is not intended to limit the scope of this patent. The scope of the present invention is pointed out in the appending claims.

RELATED APPLICATIONS

This application is related to and claims priority to U.S. ProvisionalPatent Application Ser. No. 62/404,094 filed on Oct. 4, 2016, the entirecontents of which are herein incorporated by reference.

BACKGROUND

In the manufacture of micro-scale or nano-scale devices, variousfabrication processes are executed and repeatedly performed to createfunctional device elements on a substrate. Examples of micro-scale ornano-scale devices include semiconductor devices, electronic devices,mechanical devices, etc. Examples of fabrication processing includeprocesses for film-forming, etching, patterning, cleaning, doping,annealing, treating, planarizing, etc.

Typically, these devices are produced as part of a layered devicefabrication process of, for example, a substrate (e.g., a semiconductorwafer). In some instances, a coating is “spun-on” to the substrate toform a uniform layer or film. Spin coating a material enhances itsuniformity in coverage and planarization. As used herein, planarizationor planar refers to the consistent flatness of a layer or film.

Spin coating (or spin-on coating) is a procedure used to deposit uniformthin films to flat substrates (e.g., semiconductor wafer). Usually, asmall amount of coating material is applied on the center of thesubstrate, which is either spinning at low speed or not spinning at all.The substrate is then rotated at high speed in order to spread thecoating material by centrifugal force. A machine used for spin coatingis called a spin coater, or simply spinner.

Rotation is continued while the fluid spins off the edges of thesubstrate, until the desired thickness of the film is achieved. Theapplied solvent is usually volatile, and simultaneously evaporates. So,the higher the angular speed of spinning, the thinner the film. Thethickness of the film also depends on the material properties, such asthe viscosity and concentration of the solution and the solvent.

Traditionally, the micro- and nano-fabrication of semiconductortransistors are formed in-plane—thus are often referred totwo-dimensional (2D) or planar devices. When formed, the semiconductortransistors are interconnected via metallization/wiring layers formed inoverlying layers of circuitry. While scaling efforts have greatlyincreased the number of transistors per unit area in 2D circuits, thescaling efforts introduce new and greater challenges as scaling enterssingle digit nanometer-scale device features.

In addition, device fabricators have expressed a desire forout-of-plane, or three-dimensional (3D), non-planar devices. Thedecreasing scales for fabrication coupled with the ascension of devicefeatures into the third dimension have led to increasingly complextopography. Thus, it is more difficult than ever to achieveplanarization.

SUMMARY

Described herein are technologies to facilitate device fabrication,especially those that involve spin-on coatings of a substrate (e.g.,wafer). More particularly, technologies described herein facilitate theplanarization (i.e., flatness) of spin-on coatings during the devicefabrication to form a uniformly planar film or layer on the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example scenario in which one or moreimplementations of the technology described herein may be incorporated.

FIG. 2 provides a flow chart illustrating a method of facilitatingplanarizing a substrate in accordance with the technology describedherein.

FIG. 3 illustrates a substrate and the length scales of interest and theplanarization signatures expected in accordance with the technologydescribed herein.

FIG. 4 provides a flow chart illustrating a method of calibrating a filmcoating model over topography and designing test structures formetrology and calibration in accordance with the technology describedherein.

FIG. 5 provides examples of test structure designs for model calibrationin accordance with the technology described herein.

FIG. 6 provides examples of three-dimensional (3D) structures inaccordance with the technology described herein.

FIG. 7 illustrates a model calibration methodology for multiple scalesof interest in accordance with the technology described herein.

FIG. 8 provides a flow chart and illustration depicting a method forcalibrating a film coating model over topography on a substrate inaccordance with the technology described herein.

FIG. 9 provides a flow chart illustrating a method of applying acalibrated spin coating model to predict film thickness in accordancewith the technology described herein.

FIG. 10 provides an illustration of a cross-section of a substrate and afilm along with relevant terms, which help with the explanation ofimplementations of the technology described herein.

FIGS. 11-12 provide flow charts illustrating a method of applying acalibrated spin coating model, including a feed-back methodology forelectronic design automation and a feed-forward methodology for unitprocessing in accordance with the technology described herein.

The Detailed Description references the accompanying figures. In thefigures, the left-most digit(s) of a reference number identifies thefigure in which the reference number first appears. The same numbers areused throughout the drawings to reference like features and components.

DETAILED DESCRIPTION

Described herein are technologies to facilitate device fabrication,especially those that involve spin-on coatings of a substrate (e.g.,wafer). More particularly, technologies described herein facilitate theplanarization (i.e., flatness) of spin-on coatings during the devicefabrication to form a uniformly planar film or layer on the substrate.

Typically, with device fabrication, it is desirable to achieve a uniformplanarization (i.e., flatness) of spin-on coatings across the substrate.That is, the film that results from the spin-on coating should have auniformly flat surface. The resulting uniformity (or lack thereof) offlatness is affected or achieved by many planarization-enhancing factorsand actions. Such factors/actions include material properties,underlying topography, and post-application smoothing.

The properties of the materials applied to a substrate affect theresulting flatness of the final layer. Examples of such propertiesinclude the viscosity of the coating being dispensed, the amount ofmaterial, the location of the material on the substrate, and thetiming/speed/acceleration of the spin.

In addition, the underlying topography of the substrate affects theuniformity of the film. Typically, features are etched into thesubstrate to form the devices. This etching forms a specific topographyon the resulting surface. Because of this, this etched or patternedsurface is called the “feature topography” herein. Subsequently, thenext spin-on coating is applied to the feature topography. Since thefeature topography is not a flat surface, the features affect thecoating application and ultimately the uniformity of the resulting film.

Moreover, after a film is applied to a substrate, the film may benor-uniform. This non-flat film can be fixed after application of thecoating Either mechanically or chemically. That is, the rough or bumpyfilm may be polished using the appropriate chemicals and/or with amechanical “polisher.”

While these actions and options are available to enhance and facilitatethe planarization of a spin-on film, there is no existing technology toeffectively predict the non-uniformity of the next to-be-applied layer(given known conditions). Consequently, no existing technology offersrecommendations for planarization-enhancing factors and actions that maybe employed to ameliorate a predicted lack of flatness of the nextto-be-applied layer.

However, one or more embodiments of the technology described herein mayeffectively predict the non-uniformity of the next to-be-applied layer(given known conditions). With this prediction, one or more embodimentsmay generate and recommend (or automatically implement) particularplanarization-enhancing factors and actions that may be employed toameliorate a predicted lack of flatness of the next to-be-applied layer.

For example, one or more embodiments may suggest or implementadjustments/selection of materials or in the application of thatmaterial. Alternatively or in addition, one or more embodiments maysuggest or implement hardware solutions, such as chemical and/ormechanical smoothing of a non-planar film. Alternatively or in addition,one or more embodiments may suggest or implement a re-design of featuresof an underlying surface.

The technology described herein can facilitate the creation anddevelopment of a comprehensive film thickness spin coat model overpatterned topography including all length scales of relevance. Theability to predict film thickness outcomes over patterned topography forany design, process, and material combination is very powerful asmanufacturing technologies become more reliant on 3D structures (e.g.,finfets, through silicon vias, gate all around, etc.). This technologymay lead to control loops to feed back or forward this information intoprocess correction capabilities, design improvements and will ultimatelylead to increases in product yield.

The micro- and nano-scale electronics processing to build integratedcircuits requires multiple film coatings over patterned topography.Deviations in film thickness for spin-on coatings over patternedtopography often drive downstream processing beyond requiredspecifications. The three (3) length scales of interest are substratescale, die scale, and feature scale. A detailed understanding andsimulation of film coating thickness over topography at these differentlength scales at positions across the chip stack can allow forcorrections in a number of downstream processes.

Unit operations having errors introduced due to deviations in filmthickness height include but are not limited to: lithographic CD(critical dimension) changes due to reflectivity, lithographic focuscontrol, etch depth, and subsequent deposition processes. Additionally,novel 3D applications and processes such as pattern reversals andexhuming materials post spacer processes may require stringent levels offilm thickness control over topography.

The simulation and knowledge of film thickness over patterned topographyare based on, for example, incoming pattern density, planar filmthickness, material properties, and spin on process conditions. Thedescribed technology includes a method of calibrating a model or modelsto accurately predict spin on film thickness over patterned topography.Three length scales of interest in semi-conductor design and processingare discussed. A method to design test structures on an experimentalmask set to be used for coating model calibration is described herein,along with metrology options. Creating a data sample plan is explainedacross the length scales of interest, and the method to fit a patterndensity model is described in detail along with the mathematical formsthat can be used.

The method to calibrate or predict film thickness may be used forblanket films applied to the patterned substrate to account thicknessvariations related to pattern density and the properties of the appliedfilm. Further, the methods described herein may also apply to blanketfilms which receive post-spin on processing such as an etch back process(e.g., wet or dry), a UV treatment, a thermal treatment, a chemicaltreatment, or a combination thereof. In this embodiment, the blanketfilm may be deposited on the wafer, and undergo additional treatmentsprior to subsequent lithography processing. Hence, the patterndependencies of the blanket film, the treated film, or a combinationthereof may be modeled using the techniques disclosed herein.

Example Scenario

FIG. 1 illustrates an example scenario 100 in which one or moreimplementations of the technology described herein may be incorporated.The example scenario 100 includes a functional representation 110 of anexample implementation of the technology described herein and afabrication 160 of a semiconductor wafer (which is an example of asubstrate fabrication contemplated for use with the technology describedherein.)

As depicted, the fabrication 160 includes an etching 170 section, aspin-coating 180 section, and an intermediate/final stack or holding bin190. These sections of this fabrication 160 are merely intended torepresent the portions of a typical fabrication that are most relevantto the example implementation related to this figure. It does notrepresent all sections or portions of a suitable fabrication for this orother implementations of the technology described herein. Furthermore,the order of the sections of the fabrication 160 is offered forillustration purpose only and it does not represent any required ornecessary order for this or any other implementation.

As depicted, the etching 170 includes a wafer 172 in an etch chamber 174being etched (e.g., via plasma). For example, with plasma etching, aplasma 176 removes material from the surface of the wafer 172. Theplasmas of the process gasses convert the material to be etched from thesolid to the gaseous phase, and the vacuum pump (not shown) extracts thegaseous products. The use of masks can also ensure the etching of onlyparts of the surface or structures. The etching process is controlledand monitored by one or more computer systems 178.

At least some of the techniques described herein pertain to devicefabrication using precision etch techniques. Several instances manifestin semiconductor manufacturing in both front end of the line (FEOL,e.g., transistor fabrication) through to the back end of the line (BEOL,e.g., interconnect fabrication), where oxide and nitride films(typically silicon-containing, in nature) need to be etched with a highdegree of precision.

As depicted, the spin-coating 180 includes a spinning wafer 182 in acoating chamber 184. For example, a coating 186 may be dispensed ontothe surface of the wafer 182. Ideally, the spin-coat material will forman even or uniform layer on the wafer 182. The spin-coating process iscontrolled and monitored by one or more computer systems 188.

The intermediate/final stack or holding bin 190 represents a collectionof wafers (such as wafer 192) that has completed the fabrication processthat includes repeated etching and coating processes. Alternatively, theholding bin 190 may hold wafers as an intermediate step of thefabrication process.

The functional representation 110 of the example implementation of thetechnology described herein includes four functional sections. Each ofthese sections interacts with some portion of the fabrication 160. Thefour functional sections include model creation 120, planarizationprediction 130, remedy suggestion 140, and remediation 150. Each ofthese functional sections interacts with other sections and with one ormore portions of the fabrication process and components. The details ofeach section are described below in portions of the document that focuson each section.

However, in short, the model creation 120 involves the generation of amodel of the feature topography of an etched wafer. That is, a computersystem generates a computer-generated 3D rendering of the many featuresof an etched wafer based on design and process knowledge Example detailsthat are related to the model creation 120 are described and discussedbelow with regard toward FIGS. 2-8.

The model creation 120 includes receiving substrate patterninginformation for a patterned semiconductor substrate. Then, a topographymap of a patterned substrate is generated. That topography map is based,at least in part, on the substrate patterning information. The substratepatterning information includes feature dimensions, mask tone, or filmthickness measurement values. The topography map includes featuresvarying by height, width, and the distance between the features.

The planarization prediction 130 uses information about various materialand environmental properties to simulate the spin-coat application tothe modeled feature topology. Examples of details that are related tothe planarization prediction 130 are described and discussed below withregard toward FIGS. 9-10.

The simulation and knowledge of film thickness over feature topographyare based on, for example, incoming pattern density, planar filmthickness, material properties, and spin on process conditions. Thepattern density may, for example, be expressed in the form of a numberover a specified area. Alternatively, the pattern density may beprovided, for example, in the form of a surface map indicating localpattern density values at locations in the mask field.

Examples of planar film thickness includes 100 nm or 2 um. The planarfilm thickness may be expressed as a height over a distance value.Examples of material properties includes density, viscosity, surfacetension, and vapor pressure. Examples of spin-on process conditionsincludes spin speed of 2000 RPM and post apply bake of 60 sec at 100 C.

A method of coating a substrate with a planarization film, includingmethods of calibrating a model or models to accurately predict spin onfilm thickness over patterned topography, is described herein. Multiplelength scales of interest in semi-conductor design and processing arediscussed. The method to design test structures on an experimental maskset to be used for coating model calibration is described herein, alongwith metrology options. Creating a data sample plan is explained acrossthe length scales of interest, and a method to fit a pattern densitymodel is described herein along with the mathematical forms that can beused. Furthermore, a feed-back methodology for electronic deviceautomation and a feed-forward methodology for unit processing aredescribed herein.

The planarization prediction 130 includes receiving substrate patterninginformation and a film thickness model based, at least in part, on athickness of a film being deposited on the patterned substrate and anarrangement of features on the patterned substrate. The planarizationprediction 130 also includes generating a film thickness model (i.e., asimulation of film thickness) of the patterned substrate based, at leastin part, on the substrate patterning information and the film thicknessmodel.

The film thickness data is associated with a film deposited on thesemiconductor substrate. The model of the film thickness is a model forthe semiconductor substrate that is based, at least in part, on theplurality of film thickness points. The model of film thickness includesan estimated film thickness based, at least in part, on a blanket filmthickness, a localized pattern height, a localized pattern width, and alocalized density of features within the patterned substrate. Theplurality of film thickness data includes thickness data of one or morefilms on the semiconductor substrate. The film includes a blanket film,a patterned film, or a treated film.

Generating the deposited film thickness model involves: assigning gridpoints across the patterned substrate; determining a trench depth at oraround the grid points on the substrate; setting a calculation distancefrom the grid points; and determining a film thickness for the gridpoints based, at least in part, on a blanket film thickness, the trenchdepth proximate to the grid point, a surface area around the grid point,and values from adjacent grid points within the calculation distance ofthe target grid point.

The arrangement of features is based, at least in part, on one or moreof the following: feature depth, feature width, or feature surface areaat different locations across the patterned substrate.

The planarization prediction 130 also includes: comparing the depositedfilm thickness model to a predetermined specification; adjusting one ormore process conditions based, at least in part, on the comparing of thedeposited film thickness model and the predetermined specification.

The process conditions include one or more of following: spin speed fora film being deposited on a substrate, focus or dose of a lithographyprocess used to pattern the substrate, etch time, or etch power.

The planarization prediction 130 also includes: comparing the depositedfilm thickness model to a predetermined specification; adjusting one ormore process targets based, at least in part, on the comparing of theprocess simulations with the predetermined value.

The process targets include one or more of the following: depositionthickness, trench depth, film non-uniformity.

The planarization prediction 130 also includes: comparing the depositedfilm thickness model to a predetermined specification; adjusting one ormore design conditions based, at least in part, on the comparing of thedeposited film thickness model and the predetermined specification.

The design conditions include one or more of following: device layout,dummy fill layout, mask layout, or other conditions that impact patterndensity on the patterned substrate. The plurality of film thickness dataincludes thickness data of one or more films on the semiconductorsubstrate. The film includes a blanket film, a patterned film, or atreated film.

Based upon calibration model of the model creation 120 and theprediction of the planarization prediction 130, the remedy suggestion140 generates one or more recommendations to facilitate or enhanceplanarization of the spin-on coating for that feature topology. Examplesdetails that are related to the remedy suggestion 140 are described anddiscussed below with regard toward FIGS. 10-11.

The remedy suggestion 140 includes a determination of the film thicknessof an area of the film-thickness model falls with a defined range. Forexample, in some implementations the film thickness measurements have adefined range from 95 nm to 105 nm. For example, with that definedrange, if the film thickness over topography is measured to be 93 nm,then corrective action would be taken. Then, based upon thatdetermining, the area of the film-thickness model is declared to beplanar. If not, then remedies are suggested that will enhanceplanarization of that area of the film-thickness model. The remediesaffect the substrate fabrication.

Moreover, remediation 150 involves action being taken based on therecommendations of the remedy suggestion section. Such action may beautomatic, manual, or some combination thereof. Examples details thatare related to the remediation 150 are described and discussed belowwith regard toward FIGS. 10-11.

Model Creation

FIGS. 2-8 illustrate and demonstrate example processes and detailsrelated to the model creation 120 of FIG. 1.

FIG. 2 illustrates an example high-level flowchart of an implementationof the creation of a calibration model (such as model creation 120 ofFIG. 1). More particularly, FIG. 2 shows an example process 200 forcalibrating a film thickness model over patterned topography. Theprocess 200 may be implemented using one or more computer systems.

At 210, the computer system employs a design of appropriate teststructures on a mask. In some implementations, such a design may becreated or supplied, at least in part, design system or createdmanually.

At 212, the computer system implements an appropriate metrology/samplingplan for data collection. In some implementations, this plan may beprovided and/or created planning system or created manually.

At 214, the computer system collects thickness data across length scalesof interest. The scales of interest is discussed below with regard toFIG. 3.

At 216, the computer system determines, based on the signatures observedor analyzed, the appropriate model forms that best-fit the data.

At 218-220, the data is input in model calibration algorithms and basedon target residuals can be moved through an iterative process to fit themost appropriate model forms and parameters.

At 222, the model is verified with additional data and/or processconditions.

FIG. 3 demonstrates that developing a comprehensive film thickness modelover topography involves consideration of appropriate length scales.Substrate scale effects, across mask effects, and pattern specificcoating signatures are factors to feed forward to an availablecorrective process.

The substrate scale is demonstrated at 310. At the substrate scalecharacterizing film, coating differences require a center to edgemeasurement signature over identical patterns in the mask field. Themask field pattern density contributes to the film thickness signatureover the topography.

The die scale is demonstrated at 330. The die scale (which is alsocalled midrange length scale) is characterized by similar local trenchsizes with varying pattern density over the mask filed.

The feature scale is demonstrated at 350. The feature scale representsthe smallest scale of interest. The feature scale is the thicknessmeasurements over patterned features. While it is common for the featurescale to be below 1000 nm in many implementations, the actual scale isdependent on the specific application and specific design rules.

FIG. 4 illustrates an example process 400 for the design of teststructures. As part of the model calibration process of the modelcreation 120, test structures are designed and placed on an experimentalmask that can be used for film thickness metrology. Design constraintstypically center around metrology, process, materials, and availablearea on the mask. Metrology options for feature scale, and die scalelength considerations may involve, but are not limited to: TEM(transmission electron microscope) cross-section, SEM (scanning electronmicroscope) cross-section, profilometry, PWG (patterned wafer geometry),scatterometry, etc.

At 410, a computer system determines or employs determined metrologyconstraints. Such constraints include the field of view, sampling rate,resolution, precision, etc. From this various metrology, options areavailable. Examples of such options include TEM, SEM cross section,profilometry, ellipsometry, PWG (patterns wafer geometry) andscatterometry.

At 412, the computer system confirms possible length scale ranges basedon material and processes of interest. In some instances, the materialsand applications may not have varied thickness over particular lengthscales. In those instances, perhaps less than three length scales aredesirable. For instance, a spin on carbon material may exhibit differentthicknesses that require modeling over topography at feature scale, butnot over larger areas such as die scale or wafer scale. With anothermaterial and application, for example, a spin on dielectric materialused over more complicated topography may exhibit different trends overfeature scale, die scale and wafer scale, and therefore it would bedesirable to have a calibrated model taking into account all of thoselength scales. In other words, advance knowledge of process,application, and material helps determine where film thicknessmeasurements are helpful to properly calibrate a model.

At 414, the computer system specifies trench test patterns in anindustry standard file format for circuit design data or mask data(e.g., GDS or graphic database system format) to accommodate severaltest patterns and length scales for model/process calibration. That is,the drawing test structures are stored in a design file and then thisdesign file is transferred to a mask that can be used to process thetopography structures and then later measure film thicknesses for modelcalibration. During this operation, the computer system createsdifferent topography design structures to span enough variation to getsufficient information for calibrating a model.

At 416, the computer system produces the results that indicatestructure. Examples of such results includes step height jso-trench,dense pitch, and variable surrounding pattern density. The step heightrefers to a situation where there is only one step change in topography.This is basically the simplest topography feature one could have wherethe film transitions over one step change only. The iso-trench is anisolated trench. This is essentially two step heights or one singletrench, and this is the next simplest topography trench structure tomodel. A dense pitch drawing involves several trenches drawn closetogether.

All of these structures could be surrounded by “variable patterndensity.” The variable pattern density indicates the density of thetrenches that surrounds the specified structures. For example, thesurrounding area may have no trenches, all trenches (100% trenches), oryou could have some varied percent of trenches to test how the materialfills different surrounding areas. As an analogy, consider a riverduring a flood. If there are many trenches and low areas around theriver the water will go there. If there are no areas as low as the riverbed, the water will spread, travel far and flood quickly. So, thepercentage of low lying areas for the water to flow to around the riveraffects how the water gets distributed

FIG. 5 demonstrates a variety of example test patterns that can be usedfor feature scale and mask scale model calibration. Certain specificstructures should be available on the mask when considering thecalibration of the model.

Example pattern 510 is a height structure used for characterizing 1Dfilm transition over the maximum topography height. Example pattern 512is a large area of constant pattern density, which will be characterizedby an appropriate metrology tool, (e.g. PWG), and these types ofstructures are particularly relevant for characterizing mask scalesignatures. Additional types of patterns include isolated or densetrenches surrounded by variable pattern densities at flexible radialdistances around metrology points of interest. For example, patterns 514a and 514 b demonstrate isolated trench in varied patterns densities,and example pattern 516 shows dense pitch structures surrounded byvariable pattern density.

Another type of pattern is 1D pitch variations, including isolated anddense structures. These designs are created for large field of view SEMcross sections to characterize feature scale changes in one capturedimage. An example of that is patterns 518 a and 518 b showing variationin feature pitch at minimum length scales.

FIG. 6 shows a top-down view of a trench design (i.e., mask) at 610.Views 612-616 shows alternative cross-section views of a resultingfeature topography after etch processing of the same trench design 610.View 612 shows a single depth trench with a depth of d. View 614 shows aresulting feature topography using the same mask as 612 but with adifferent etch process that produces a different trench depth of d′.View 616 shows another different feature topography using the same maskas 612 but with a trench having different stepped depths.

This illustrates the concept of creating alternate 3D trench structuresfrom the same 2D test structure mask design. For example, using amodified etch process could create a deeper trench providing a newcalibration structure and additional thickness data for modelcalibration. This demonstrates using multiple patterning processes tocreate varying trench depths, creating new topography features andmultiple metrology points for calibration over a single trench as viewedfrom the top down.

Developing a metrology sample plan for model calibration andverification is dependent on understanding coating responses at lengthscales of interest. The feature scale metrology sample plan shouldinclude the structures defined in FIG. 5 along with some base structures(i.e. step height and isolated trench) that can be used for across maskand/or across wafer metrology.

FIG. 7 shows an example process 700 for defining an appropriate sampleplan. At 710, a computer system determines feature scale metrologypoints from structures (such as those shown in FIG. 4). This includesbase structures for sampling across mask/wafer. Mask 712 and feature 714illustrate examples of the scale at which this action operates.

At 720, the computer system determines across-mask metrology samplingfrom base structures as well as large area pattern density samples. Anexample of this is shown at 722. Base structures are sampled across themask field (e.g. cross-section SEM or profilometry). The defined areapattern density structures are sampled across the mask field (e.g. PWG).

At 730, the computer system determines across wafer metrology samplingfrom base structures as well as large area pattern density samples. Thisis depicted at 732. This action involves sampling a consistent patternwithin mask locations across the wafer, identifying potential radialsignatures and accounting for other known post processing signatures(e.g., signatures, etch back, or UV illumination).

After base feature structures are identified an across mask sample plancan be determined, and large area structures can also be sampled acrossmask. Appropriate statistical sampling should prove the absence orpresence of any across mask signature, and verify the length scales atwhich pattern density values affect coating thickness. Likewise, thesemeasurements can be sampled across the wafer looking for radialsignatures and taking into account any other known processing signaturesthat may exist.

FIG. 8 illustrates a processing method for model calibration. After asample plan is defined and metrology is completed on a desiredmaterial/process combination.

At 810, a computer system collects metrology values and locations andthen the system collates design files (GDS) or mask files with trenchpatterns and surrounding patterns to provide relevant inputs. Examplesof such input include feature design dimensions, GDS clips withsurrounding pattern density, mask tone, and film thickness measurementvalues, metrology, trench patterns/pattern density, and mask tone.Examples of such is shown at 812, which shows a simplified version ofthe graph depicted in FIG. 10 and described later.

At 820, the computer system converts the design file shapes (labeled atGDS data) into binary text files on a user defined grid (e.g., locationsof trenches). Metrology values are input into a mirrored text file on anidentical grid. Box 822 illustrates the actions of block 820.

At 830, the computer system obtains input regarding film thicknessmeasurement values and locations that match the defined pattern.

At 840, the computer system applies the pattern density models to obtainthe best-fit parameters. This may be accomplished through a minimizationroutine (e.g., script) such as Nelder-Mead. Here, the best-fit algorithmis used to fit the best values from floating parameters and output modelerror relative to experimental data. Details on the functional form ofpattern density models are discussed below with regard to FIG. 9.

One possible functional form of the film height related to an x, y gridis the sum of a constant multiplied by a selectable proximity functionconvoluted with trench x, y locations within the grid. One example of aproximity function is shown in the Gaussian form. In this form, thetrench depth, as well as a search radius, are shown to relate trenchlocations to film height above those coordinates. This is one example ofa functional form that can be used in a minimization routine to providebest-fit parameters and ultimately one mathematical description of afilm height over trench topography.

Planarization Prediction

FIGS. 9 (in full) and 10 (partially) illustrate and demonstrate exampleprocesses and details related to the planarization prediction 130 ofFIG. 1. FIG. 9 demonstrates an example process 900 for applying thecalibrated model to a new design file.

At 910, a computer system obtains various inputs, such as design data,appropriate tone (positive/negative) of design topography, trenchthickness as a function of design input or constant, grid size, and thecalibrated film thickness model.

At 912, the computer model converts the file of design data from oneformat to another. The topography design data is typically file formatspecifically associated with such data. Examples of such file formatsinclude GDS, Oasis, etc. The design data file is converted to a“normalized” file format (e.g., text file) with trench locations on achosen input grid.

At 914, the computer system performs computations using, for example,Equation 1 (below) across the converted design file.h(x,y)=h ₀ +ΣC _(i) p(x,y)*Tr(x,y)  Equation 1

-   h(x, y)=film z height at given x, y location-   h_(o)=constant, representing blanket film thickness with no    topography-   C_(i)=constant-   p(x, y)=selectable proximity function-   Tr(x, y)=Trench pattern locations

${p\left( {x,y} \right)} = {\frac{d}{{\pi\sigma}^{2}}e^{\frac{- {({x^{2} + y^{2}})}^{1/2}}{\sigma^{2}}}}$

-   d=trench depth-   σ=search radius

This equation and its variables are shown in FIG. 10. Of course, otherimplementations may utilize other equations.

FIG. 10 depicts a simplified cross-section 1000 of a portion of asubstrate 1020 with an etched layer thereon. The etched layer hasfeatures such as 1022 and 1024. A blanket coat 1030 is shown over thelayer and the features of the layer. The figure also shows thedefinitions of various terms used in this illustration. Here, theconverted design file is read as input. A calculation distance from eachgrid point is set as input. This allows calculations to take intoaccount trench placements within that radius.

Typically, this should be set greater than a. In practice, 3 σ is a goodchoice. For each grid point, the calculation distance defines an area ofthe other grid points included in the calculation. Equation 1 is appliedto each individual grid point, using surrounding grid point values withthe calculation radius, resulting in a film thickness value at each x, ygrid point. The calculated thickness values at each x, y grid locationare output to an output file.

At 916, the computer system generates output (typically, as a text file)that represents the spun on film height at x, y locations at each gridpoint in the provided design file. This can also be represented in3-dimensional form with utilities such as MATLAB®.

FIG. 11 illustrates example process 1100 to demonstrate feed backwardand feed forward applications. Example process 1100 continues from theoutput operation 916 of process 900.

At 1110, a computer system compares the thickness output of operation916 of FIG. 9 to initial assumptions and specifications. That is, thesystem determines how the thickness determination of process 900compares to the procedure's assumptions and provided specifications. Indoing so, the system determines if any film thickness or overalldeviation in film thickness is beyond desired ranges.

At 1120, the computer system performs downstream process simulationsbased on the film thickness map input (from process 900). Based on this,the system determines if process outputs are out of specification due toincoming deviations in film thickness. That is, the system predicts howplanar the resulting film will be across the expanse of the film.

Operations 1110 and 1120 are part of the planarization prediction 130 ofFIG. 1. Thus, operation 1120 is the result of the planarizationprediction 130. The next operations (1130 and 1140) are part of theremediation suggestion 140 of FIG. 1.

At 1130, the computer system determines remediation for planarization ofa simulated film applied to a feature topology described the inputs of910 of FIG. 9. That is, the system determines what actions orcombinations of actions that would encourage or facilitate planarizationof the simulated film—and, then ultimately, to an actual spin-coatapplied under the remediated conditions. Example remedial actions willbe discussed below with regard to FIG. 12.

At 1140, the computer system suggestions a remedial action or somecombination of such action. This suggestion may include a user-interface(UI) that provides textual and/or graphical recommendations of thesuggested actions that an operator may take manually orsemi-automatically. An operator may select one or more of the suggestedactions that are subsequently performed automatically orsemi-automatically. These suggestions are offered to operation 1210 ofFIG. 12.

FIG. 12 illustrates and demonstrates example process related to theremediation 150 of FIG. 1. FIG. 9 demonstrates an example process 1200for planarization remediation of the feature topography of the wafer.

At 1210, a computer system receives remediation suggestions fromoperation 1140 of FIG. 11 and/or information regarding planarizationdetermination performed by operation 1120. Based on this, the systemdetermines the kind and/or amount of adjustment to be performed thatwill facilitate and encourage planarization (i.e., flatness) of the filmon the feature topography of the wafer. In some ways, the functions ofthis operation 1210 are similar to those performed by operation 1130 and1140. Therefore, in practice, the functionalities of operations 1210,1130, and 1140 may be combined in some effective manner.

A feedback loop 1220 is activated when there is a determination thatplanarization may be improved by, at least in part, a change to thephysical arrangement of the feature topology in a manner that does notchange its operational parameters. That is, the triggering determinationincludes a change in pattern topography that does not affect thefunctionality of the resulting devices of the wafer.

This involves an adjustment in design, mask, or other feature shapemanipulation that is, at least in part, an effective manner tofacilitate planarization. In that instance, the process continues tooperation 1220 and forms a feedback loop 1220 with operation 910 of FIG.9. In this situation, information about the simulated film beingnon-planar is fed back to operation 910 of the process 900 to facilitateadjustment of that process. This action ultimately adjusts/changes anactual fabrication process of the fabrication 160. In so doing, theadjusted design will lead to a new feature topography to simulate.

The information is used in the feed backward loop 1220 to makeadjustments in design, mask, or other shape manipulations in the dataprep flow, such as shapes placed only for processing purposes with noelectrical functionality. The adjustments may be to the design, dummyfill, or other mask/EDA (electronic design automation). Theseadjustments change the pattern density to bring the process simulationsinto the specification.

Alternatively, a feed forward loop 1230 is activated to improveplanarization in some way other than a re-design that will not affectthe resulting functionality of the devices of the wafer.

In the alternate feed forward loop 1230, out of specificationinformation or process simulations is used to indicate controltightening for subsequent unit processes. That is, a change in theoperation of some portion of the fabrication 160 follows the creation ofthe simulated feature topography. The system directs an adjustment tosubsequent fabrication process controls to compensate for out ofspecification film thickness or other non-flat aspects of the simulatedfilm.

There are many different actions that could be directed and taken. Theexamples may include adjusting spin-on coating process (e.g., spinvelocity, the amount of coating applied, the rate of coating applied,spin acceleration, deposit location(s), etc.), baking process, orsequence of spin process steps. Another example includes adjustinglithography scanner process to control focus/dose. Still another examplemay involve adjustments to the etch process to compensate for materialthickness (or lack thereof). That is, film height control duringetching. Another still involves adjustment to downstreamcoating/deposition processes to help balance total planarization overtopography. This helps with the overall planarization of the layerstack. Of course, other remedial actions are available.

Additional and Alternative Implementation Details

“Substrate” or “target substrate” as used herein generically refers toan object being processed in accordance with the invention. Thesubstrate may include any material portion or structure of a device,particularly a semiconductor or other electronics device, and may, forexample, be a base substrate structure, such as a semiconductor wafer,mask, or a layer on or overlying a base substrate structure such as athin film. Thus, the substrate is not limited to any particular basestructure, underlying layer or overlying layer, patterned orun-patterned but rather, is contemplated to include any such layer orbase structure, and any combination of layers and/or base structures.The description may reference particular types of substrates, but thisis for illustrative purposes only.

Reference herein to “one embodiment” or “an embodiment” refers to one ormore features, structures, materials, or characteristics described atleast one example embodiment of the technology described herein. It doesnot denote or imply that the features, structures, materials, orcharacteristics are present in every embodiment. Thus, the appearancesof the phrases “in one embodiment” or “in an embodiment” in variousplaces throughout this document are not necessarily referring to thesame embodiment of the technology. Furthermore, the features,structures, materials, or characteristics may be combined in anysuitable manner in one or more embodiments.

In the above description of example implementations, for purposes ofexplanation, specific numbers, materials configurations, and otherdetails are set forth to explain better the present invention, asclaimed. However, it will be apparent to one skilled in the art that theclaimed invention may be practiced using different details than theexample ones described herein. In other instances, well-known featuresare omitted or simplified to clarify the description of the exampleimplementations.

The inventors intend the described example implementations to beprimarily examples. The inventors do not intend these exampleimplementations to limit the scope of the appended claims. Rather, theinventors have contemplated that the claimed invention might also beembodied and implemented in other ways, in conjunction with otherpresent or future technologies.

Moreover, the word “example” is used herein to mean serving as anexample, instance, or illustration. Any aspect or design describedherein as “example” is not necessarily to be construed as preferred oradvantageous over other aspects or designs. Rather, use of the wordexample is intended to present concepts and techniques in a concretefashion. The term “techniques,” for instance, may refer to one or moredevices, apparatuses, systems, methods, articles of manufacture, andcomputer-readable instructions as indicated by the context describedherein.

As used in this application, the term “or” is intended to mean aninclusive “or” rather than an exclusive “or.” That is unless specifiedotherwise or clear from context, “X employs A or B” is intended to meanany of the natural inclusive permutations. That is if X employs A; Xemploys B; or X employs both A and B, then “X employs A or B” issatisfied under any of the preceding instances. Also, the articles “an”and “an” as used in this application and the appended claims should beconstrued to mean “one or more,” unless specified otherwise or clearfrom context to be directed to a singular form.

These processes are illustrated as a collection of blocks in a logicalflow graph, which represents a sequence of operations that can beimplemented in mechanics alone or a combination of hardware, software,and firmware. In the context of software/firmware, the blocks representinstructions stored on one or more computer-readable storage media that,when executed by one or more processors, perform the recited operations.

Note that the order in which the processes are described is not intendedto be construed as a limitation and any number of the described processblocks can be combined in any order to implement the processes or analternate process. Additionally, individual blocks may be deleted fromthe processes without departing from the spirit and scope of the subjectmatter described herein.

The term “computer-readable media” is non-transitory computer-storagemedia. For example, non-transitory computer-storage media may include,but are not limited to, magnetic storage devices (e.g., hard disk,floppy disk, and magnetic strips), optical disks (e.g., compact disk(CD) and digital versatile disk (DVD)), smart cards, flash memorydevices (e.g., thumb drive, stick, key drive, and SD cards), andvolatile and non-volatile memory (e.g., random access memory (RAM),read-only memory (ROM)). Similarly, the term “machine-readable media” isnon-transitory machine-storage media. Likewise, the term“processor-readable media” is non-transitory processor-storage media.

A non-transitory machine-readable storage medium can cause a machine toperform the functions or operations described, and includes anymechanism that stores information in a form accessible by a machine(e.g., computing device, electronic system, etc.), such asrecordable/non-recordable media (e.g., read-only memory (ROM), randomaccess memory (RAM), magnetic disk storage media, optical storage media,flash memory devices, etc.). A communication interface includes anymechanism that interfaces to any of a hardwired, wireless, optical,etc., medium to communicate to another device, such as a memory businterface, a processor bus interface, an Internet connection, a diskcontroller, etc. The communication interface is configured by providingconfiguration parameters or sending signals to prepare the communicationinterface to provide a data signal describing the software content. Thecommunication interface can be accessed via one or more commands orsignals sent to the communication interface.

In the claims appended herein, the inventors invoke 35 U.S.C. § 112(f)only when the words “means for” or “steps for” are used in the claim. Ifsuch words are not used in a claim, then the inventors do not intend forthe claim to be construed to cover the corresponding structure,material, or acts described herein (and equivalents thereof) inaccordance with 35 U.S.C. 112(f).

A non-transitory machine-readable storage medium can cause a machine toperform the functions or operations described, and includes anymechanism that stores information in a form accessible by a machine(e.g., computing device, electronic system, etc.), such asrecordable/non-recordable media (e.g., read-only memory (ROM), randomaccess memory (RAM), magnetic disk storage media, optical storage media,flash memory devices, etc.). A communication interface includes anymechanism that interfaces to any of a hardwired, wireless, optical,etc., medium to communicate to another device, such as a memory businterface, a processor bus interface, an Internet connection, a diskcontroller, etc. The communication interface is configured by providingconfiguration parameters or sending signals to prepare the communicationinterface to provide a data signal describing the software content. Thecommunication interface can be accessed via one or more commands orsignals sent to the communication interface.

What is claimed is:
 1. A method of facilitating spin-coat planarizationover feature topography during substrate fabrication, the methodcomprising: generating, using a data processor, a topography map for adesired pattern of features on a semiconductor substrate, the generatingof the topography map being based, at least in part, on substratepatterning information related to the desired pattern of features;generating, using the data processor, a film-thickness model forpredicting film thickness of a spin-on coating applied to the desiredpattern of features, wherein inputs for the film-thickness model includethe topography map and an estimated film thickness of the spin-oncoating applied on the semiconductor substrate according to definedcoating process parameters; generating, using the data processor, afilm-thickness output from the film-thickness model by: assigning aplurality of grid points across the semiconductor substrate, determininga trench depth at or around each of the plurality of grid points on thesemiconductor substrate based, at least in part, on the topography map,assigning a calculation distance from each of the plurality of gridpoints, and calculating a film thickness value for each grid point inthe plurality of grid points based, at least in part, on the estimatedfilm thickness, the trench depth proximate to each grid point, a surfacearea around each grid point, and film thickness values from other gridpoints within the calculation distance; determining, using the dataprocessor, whether a predicted film thickness of an area of thefilm-thickness output falls within a defined range; and based upon thatdetermining, either declaring the predicted film thickness of the areaof the film-thickness output to be planar, or generating, using the dataprocessor, suggested remedies to enhance planarization of the predictedfilm thickness of the area of the film-thickness output, wherein thesuggested remedies affect the substrate fabrication.
 2. The method ofclaim 1, further comprising: selecting one or more of the suggestedremedies; and performing the one or more selected suggested remedies. 3.A method of facilitating spin-coat planarization over feature topographyduring substrate fabrication, the method comprising: receiving substratepatterning information related to a desired pattern of features for asemiconductor substrate; generating, using a data processor, atopography map for the desired pattern of features based, at least inpart, on the substrate patterning information; receiving data regardinga plurality of film thickness points associated with a film deposited ona patterned substrate having the desired pattern of features;generating, using the data processor, a film-thickness model forpredicting film thickness for the semiconductor substrate, whereininputs for the film-thickness model include the data of the plurality offilm thickness points; and generating, using the data processor, afilm-thickness output from the film-thickness model by: assigning aplurality of grid points across the semiconductor substrate, determininga trench depth at or around each of the plurality of grid points on thesemiconductor substrate based, at least in part, on the topography map,assigning a calculation distance from each of the plurality of gridpoints, and calculating a film thickness value for each grid point inthe plurality of grid points based, at least in part, on an estimatedfilm thickness, the trench depth proximate to each grid point, a surfacearea around each grid point, and film thickness values from other gridpoints within the calculation distance.
 4. The method of claim 3,wherein the substrate patterning information comprises featuredimensions, mask tone, or film thickness measurement values.
 5. Themethod of claim 3, wherein the topography map comprises features varyingby height, width, and distance between the features.
 6. The method ofclaim 3, wherein the inputs for the film-thickness model further includethe estimated film thickness based, at least in part, on a blanket filmthickness, a localized pattern height, a localized pattern width, and asurrounding density of features on the semi conductor substrate.
 7. Themethod of claim 3, wherein the plurality of film thickness datacomprises thickness data of one or more films on the patternedsubstrate.
 8. The method of claim 3, wherein the film comprises ablanket film, a patterned film, or a treated film.
 9. A method forpredicting planarity of a spin coating process comprising: receivingsubstrate patterning information for a patterned substrate; receiving afilm-thickness model for predicting film thickness for the patternedsubstrate, wherein inputs for the film-thickness model include anestimated thickness of a film spun onto the patterned substrate and anarrangement of features on the patterned substrate; and generating,using a data processor, a film-thickness output from the film-thicknessmodel by: assigning a plurality of grid points across the patternedsubstrate, determining a trench depth at or around each of the pluralityof grid points on the patterned substrate, assigning a calculationdistance from each of the plurality of grid points, and calculating afilm thickness value for each grid point in the plurality of grid pointsbased, at least in part, on a blanket film thickness, the trench depthproximate to each grid point, a surface area around each grid point, andfilm thickness values from other grid points within the calculationdistance.
 10. The method of claim 9, wherein the estimated thickness isbased, at least in part, on the blanket film thickness and topography ofthe patterned substrate.
 11. The method of claim 9, wherein thearrangement of features is based, at least in part, on one or more ofthe following: feature depth, feature width, or feature surface area atdifferent locations across the patterned substrate.
 12. The method ofclaim 9 further comprising: comparing the film-thickness output to apredetermined specification; and adjusting one or more processconditions based, at least in part, on the comparing of thefilm-thickness output and the predetermined specification.
 13. Themethod of claim 12 wherein the one or more process conditions includeone or more of the following: spin speed for the film being deposited onthe patterned substrate, focus or dose of a lithography process used topattern the patterned substrate, etch time, or etch power.
 14. Themethod of claim 9 further comprising: comparing the film-thicknessoutput to a predetermined specification; adjusting one or more processtargets based, at least in part, on the comparing of the film-thicknessoutput with the predetermined specification.
 15. The method of claim 14wherein the one or more process targets include one or more of thefollowing: deposition thickness, trench depth, film non-uniformity. 16.The method of claim 9 further comprising: comparing the film-thicknessoutput to a predetermined specification; and adjusting one or moredesign conditions based, at least in part, on the comparing of thefilm-thickness output and the predetermined specification.
 17. Themethod of claim 16 wherein the design conditions include one or more ofthe following: device layout, dummy fill layout, mask layout, or otherconditions that impact pattern density on the patterned substrate. 18.The method of claim 9, wherein the film-thickness model includesthickness data of one or more films on the patterned substrate.
 19. Themethod of claim 9, wherein the film comprises a blanket film, apatterned film, or a treated film.